Poly(alkylene carbonate) materials, such as poly(propylene carbonate), have been recognized as a promising material for pharmaceutical and biomedical applications due to their biodegradable and biocompatible nature. One biomedical application of these materials is their ability to release gas upon decomposition. Such materials can then be bound to a target site within a patient body and triggered to release gas bubbles. The released gas can be identified by various imaging techniques, for example, by ultrasound. Using such procedure, the location of the target site can be determined as it is correlated to the gas producing region. Further, treatment of the target site can be pursued based on the established coordinates of the site.
The gas release temperature must be biocompatible and this temperature range limits the gas releasing materials that can be used. The gas releasing materials should be stable in aqueous environment in order to be transported through the body. The amount of gas formed upon triggering of the material should be high enough for sensing the gas by an imaging tool.
Poly(propylene carbonate) (PPC) can produce CO2 as its thermal degradation byproduct. However, for production of CO2 from bulk PPC, the thermal degradation process occurs at temperatures greater than about 200° C. Further, bulk PPC is not water-soluble. Additionally, the gas generated inside the PPC bulk may diffuse away to a surrounding aqueous solution. Thus, PPC was not considered to be useful as a CO2-generating material for use as a contrast agent in medical imaging and treatment.